The invention relates to novel organosiloxanyl derivatives of alkanediol monovinyl ethers, to a process for preparing these derivatives, to the use thereof for preparing organomodified siloxanes and to the use thereof as paint additives.
Hydroxyalkyl-functional polysiloxanes are commercially available (e.g. Tegopren HSi 2111, Th. Goldschmidt AG) and can easily be prepared industrially by known methods. Compounds of this kind are used, for example, as starting materials for the synthesis of silicone polyesters (U.S. Pat. No. 5,488,123). Likewise in accordance with the prior art are processes for preparing organopolysiloxanes which have on average at least one terminal or lateral group --(CH.sub.2).sub.3 OCH.sub.2 CH(X)CH.sub.2 OH, in which X can, for example, be a hydroxyl, alkoxy or amine group (DE-C-32 15 317).
In the course of these reactions of hydrogensiloxanes with 1-alkenyl alcohols, however, a side reaction which occurs is the unwanted rearrangement into the 2-alkenol, which is unreactive for hydrosilylations. Consequently, it is usually necessary in the case of such hydrosilylation reactions to employ a high excess of the alkenols, which is removed again by distillation after the end of the reaction. As is known, this problem is also encountered in the hydrosilylation reaction of hydridosiloxanes with allyl alcohol alkoxylates (U.S. Pat. No. 4,083,856). Here too, propenyl polyethers which are formed after rearrangement of the double bond withdraw almost completely from the hydrosilylation reaction and remain in the reaction mixture. As a result it is necessary first of all, in order to achieve complete conversion of the Si--H component, to start from an excess of the olefin component; in certain cases such excesses may be in the range of up to 50 mol percent. To prepare the pure hydrosilylation adducts it would also be necessary here to purify the reaction product by distillation to remove the rearrangement product. However, such purification, especially in the case of olefin components of relatively high molecular mass, is not technically feasible.
The use of 1,4-butanediol monovinyl ether as an adduct with silanes has already been mentioned in U.S. Pat. No. 5,384,342. In that document, however, the linkage is formed by way of a silicon-oxygen bond, so that the free double bond remains available for UV-induced crosslinking reactions. In this way, however, no hydroxyalkyl-functional silane derivatives are formed.